Search for the radiative transition $\chi_{c1}(3872)\to\gamma \psi_2(3823)$

TL;DR

This study conducted the first search for a specific radiative transition involving the $ ext{X}(3872)$ particle, setting an upper limit on its occurrence and challenging certain theoretical models of its structure.

Contribution

It provides the first experimental upper limit on the radiative transition $ ext{X}(3872) o ext{psi}_2(3823)$, testing charmonium state hypotheses.

Findings

No signal observed for the transition.

Upper limit on the branching ratio set at 0.075.

Results challenge the pure charmonium $ ext{X}(3872)$ hypothesis.

Abstract

Using 9.0 $\rm fb^{-1}$ of $e^+e^-$ collision data collected at center-of-mass energies from 4.178 to 4.278 GeV with the BESIII detector at the BEPCII collider, we perform the first search for the radiative transition $\chi_{c1}(3872)\to\gamma \psi_2(3823)$. No $\chi_{c1}(3872)\to\gamma \psi_2(3823)$ signal is observed. The upper limit on the ratio of branching fractions $\mathcal{B}(\chi_{c1}(3872)\to\gamma \psi_2(3823), \psi_2(3823)\to\gamma\chi_{c1})/\mathcal{B}(\chi_{c1}(3872)\to\pi^+\pi^- J/\psi)$ is set as 0.075 at the 90\% confidence level. Our result contradicts theoretical predictions under the assumption that the $\chi_{c1}(3872)$ is the pure charmonium state $\chi_{c1}(2P)$.